Effectiveness of pheromone mating disruption for the ponderosa pine tip moth, Rhyacionia zozana (Kearfott) (Lepidoptera: Tortricidae), and its influence on the associated parasite complex

Graduation date: 1989The importance of pheromones in insect control relies both on\ud their ability to reduce pest populations and on their relatively benign\ud effects on nontarget organisms. This study was conducted to test the\ud effectiveness of a pheromone application for mating disruption of the\ud ponderosa pine tip moth, Rhyacionia zozana (Kearfott), and to determine\ud if this treatment had any affect on the abundance or structure of the\ud associated parasite complex.\ud Chemical analyses, electroantennograms, and field bioassays showed\ud that the most abundant pheromone component for R. zozana was\ud E-9-dodecenyl acetate with a lesser amount of E-9-dodecenol also\ud present. Acetate/alcohol ratios averaged 70:30 in gland washes; male\ud moths were most attracted to sticky traps with synthetic baits\ud containing ratios ranging from 70:30 to 95:5.\ud Sixteen hymenopteran and one dipteran species of parasites were\ud recovered from R. zozana larvae and pupae collected in Calif. and\ud Oreg. Total percentage parasitism was high, averaging 47.2%. The\ud ichneumonid, Glypta zozanae Walley and Barron, was the most abundant\ud parasite, attacking over 30% of the hosts collected. Mastrus\ud aciculatus (Provancher) was second in abundance, accounting for less\ud than 4% parasitism.\ud Hercon laminated-tape dispensers containing synthetic sex\ud pheromone (a 95:5 mixture of E-9-dodecenyl acetate and E-9-dodecenol)\ud were manually applied on 57 ha of ponderosa pine plantations in\ud southern Oreg. The nominal dosage was 13.5 g of pheromone/ha from 100\ud releasers per hectare spaced at 10 m. Male moth response to\ud pheromone-baited traps and to virgin females showed nearly total\ud disruption of female sex pheromone communication with males. After the\ud mating-disruption application, larval populations were reduced 83.2% in\ud treated areas. The frequency of damaged terminal shoots was 50% lower\ud in pheromone treated plantations than in check plots.\ud Total percentage parasitism was not changed due to the disruption\ud treatment. However, in treated areas, abundances of G. zozanae and\ud M. aciculatus, were reduced and increased, respectively, compared to\ud check plantations. A similarity index showed that the parasite\ud community structures of check and treated areas differed more after\ud disruption than before. Accounting for parasitism and reduced mating,\ud surviving host populations in check plantations were over four times\ud greater than in pheromone disrupted areas. The importance of the\ud host's sex pheromone as a potential kairomone, and effects of changes\ud in the host density caused by the mating disruption treatment on the\ud associated parasites are discussed